"Ctrl if it's held down and pressed with another key, Escape if it's pressed and released on its own."
It works really nicely once you get used to it.
EDIT:
To do that I first mapped Capslock to Ctrl using the normal Apple Keyboard prefs, then used KeyRemap4MacBook and checked this setting: http://i.imgur.com/99cNs.png
Comments
I remapped Capslock to:
"Ctrl if it's held down and pressed with another key, Escape if it's pressed and released on its own."
It works really nicely once you get used to it.
EDIT:
To do that I first mapped Capslock to Ctrl using the normal Apple Keyboard prefs, then used KeyRemap4MacBook and checked this setting: http://i.imgur.com/99cNs.png
http://pqrs.org/macosx/keyremap4macbook/
I could definitely get used to that. Did you remap that in vim itself, or from your operating system?
How did you get your operating system to do that?